Steering assist device

Abstract

In a steering assist device, a correction gain setting unit sets correction gain to one if it determines that that the sign of a lateral deviation change rate is different from that of a second derivative value of a lateral deviation. The correction gain setting unit sets the correction gain to a predetermined value that is larger than one, if it determines that that the sign of the lateral deviation change rate is the same as that of the second derivative value of the lateral deviation. A gain multiplication unit corrects a lane keep assist current value calculated by a lane keep assist current value calculation unit by multiplying the lane keep assist current value by the correction gain set by the correction gain setting unit.

Description

INCORPORATION BY REFERENCE[0001]The disclosure of Japanese Patent Application No. 2015-120563 filed on Jun. 15, 2015 including the specification, drawings and abstract, is incorporated herein by reference in its entirety.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to steering assist devices for vehicles, and more particularly to steering assist devices that prevent a running vehicle from deviating from its lane.[0004]2. Description of the Related Art[0005]If a vehicle deviates from its lane on a highway etc. due to driver's carelessness or a road surface condition, there is a risk that the vehicle may contact other vehicle(s) or a guardrail. As a solution, lane departure warning systems are developed which obtain road surface information and relative position information between the vehicle and its lane based on an image shot by a camera mounted on the vehicle and warn the driver when the vehicle is about to deviate from its lane. Se...

AI Technical Summary

Benefits of technology

[0006]It is one object of the present invention to provide a steering assist device that can quickly return a vehicle to a target travel line when it deviates from the target travel line.

[0008]The steering assist device of the above aspect can generate lane keep assist torque that makes the lateral deviation and the lateral deviation change rate closer to zero. Since the vehicle is thus guided so as to make the lateral deviation closer to zero, the vehicle can be guided toward the target travel line. Moreover, since the vehicle is guided so as to make the lateral deviation change rate closer to zero, the vehicle can be guided so as to make a lateral centerline of the vehicle parallel to the target travel line when the vehicle is traveling near the target travel line. The vehicle can thus be guided so as to avoid deviating from its lane.

[0009]In the steering assist device of the above aspect, the lane keep assist current value calculated by the lane keep assist current value calculation unit is corrected so that the absolute value of the lane keep assist current value increases, if the lateral deviation change rate and the rate of change in the lateral deviation change rate per unit time have the same sign. The case where both the lateral deviation change rate and the rate of change in the lateral deviation change rate per unit time have the same sign corresponds to the state where the degree to which the vehicle deviates from the target travel line is increasing. The state where the degree to which the vehicle deviates from the target travel line is increasing refers to the state where both the lateral deviation and the lateral deviation change rate are changing in a direction away from zero. Accordingly, in the present invention, the lane keep assist torque can be increased in the state where the degree to which the vehicle deviates from the target travel line is increasing. The vehicle can therefore be rapidly returned toward the target travel line if it deviates from the target travel line.

Problems solved by technology

If a vehicle deviates from its lane on a highway etc. due to driver's carelessness or a road surface condition, there is a risk that the vehicle may contact other vehicle(s) or a guardrail.

Images